The present invention relates to an improvement in a wippen heel mechanism for an upright piano.
Upright pianos have heretofore been widely used becasue of their reduced size, inexpensive price and convenient operability. However, there is merit to the proposition that upright pianos are inferior to grand pianos in terms of tone volume, key touch quality, and the operation of each action mechanism for causing movement of a hammer.
For this reason, upright pianos is seldom employed for public performance such as concerts; accordingly, it is known that even a student who practices while playing an upright piano eventually employs a grand piano for practice.
Referring to FIG. 5 in which like reference numerals are used to denote like or corresponding elements shown in FIGS. 1 and 2, a conventional type of upright piano includes a known action mechanism which is arranged to transmit the motion of each piano key K to a hammer H. However, comparing such an action mechanism 7 is to the improved action mechanism 7 shown in FIG. 1 which will be described later, the wippen heel arrangement of the mechanism 7 assumes an undesirable state shown in FIG. 3. This may causes various difficulties in the assembly of a piano, and there is a risk of adversely affecting the key touch quality of a depressed key.
In general, the aforesaid action mechanism 7 functions to transmit the motion of the piano key K to the hammer H, and the wippen heel arrangement serves as an input portion for the mechanism 7. As shown in FIG. 3, in accordance with the related art, the wippen heel arrangement has a pillar 9 screwed into a piano key K for allowing the length of the projecting portion of the pillar 9 which projects from the piano key to be adjusted and a wippen heel 11 disposed in contact with the upper surface of the pillar 9. The upper surface of the pillar 9 is semispherical while the lower surface of the wippen heel 11 is substantially flat. In this arrangement, the wippen heel 11 is adapted to be moved up and down positively in accordance with any motion of the piano key K.
In such a wippen heel arrangement, however as shown in FIG. 3, the circular arc traced by the upper end of the pillar 9 intersects that traced by the lower end of the wippen heel 11 at a large angle. The higher a piano the larger, this angle of intersection becomes.
For this reason, when the piano key K is depressed, slip may take place between the pillar 9 and the wippen heel 11. Specifically, after the depression of the piano key K, a contact point a between the pillar 9 and the wippen heel 11 is caused to travel towards a point b away from a point a' at the end of upward movement of the pillar 9.
If such slip causes any unnecessary motion in the mechanism, the key touch quality of a piano becomes unsatisfactory and, in addition, there is a likelihood that a felt cover bonded to the wippen heel 11 may be damaged in a short period of time.
As shown in FIG. 4, a counterpillar 11a may be attached to the lower end of the wippen heel 11, and the lower surface of the counterpillar 11a may be provided with a concave surface complimentary to the shape of the upper surface of the pillar 9. However, this arrangement has a disadvantage in that it is difficult to attach a felt cover to such a concave surface. In particular, it is extremely difficult to attach all the felt pads to the same concave surface. Moreover, in such an arrangement, the contact point a between the pillar 9 and the counter pillar 11a is caused to travel to an upwardly right point a' about the rotational center e of the piano key K. Simultaneously, a continuous point b between the wippen heel 11 and the counter pillar 11a is caused to travel to an upwarly left point b' about the rotational center f of the wippen 12.
Accordingly, the force applied to the upper end of the pillar 9 is dispersed in the direction of C (shown in broken line) to D (shown in broken line) and thus the counterpillar 11a is forced in an inclined upward direction. This may produce the unnecessary motion and a pinch of the wippen heel arrangement, thus making it impossible to catch the hammer H.